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Title: Structure of the Photo-catalytically Active Surface of SrTiO 3

Abstract

A major goal of energy research is to use visible light to cleave water directly, without an applied voltage, into hydrogen and oxygen. Although SrTiO3 requires ultraviolet light, after four decades, it is still the “gold standard” for the photo-catalytic splitting of water. It is chemically robust and can carry out both hydrogen and oxygen evolution reactions without an applied bias. While ultrahigh vacuum surface science techniques have provided useful insights, we still know relatively little about the structure of these electrodes in contact with electrolytes under operating conditions. Here, we report the surface structure evolution of a n-SrTiO3 electrode during water splitting, before and after “training” with an applied positive bias. Operando high-energy X-ray reflectivity measurements demonstrate that training the electrode irreversibly reorders the surface. Scanning electrochemical microscopy at open circuit correlates this training with a 3-fold increase of the activity toward the photo-induced water splitting. A novel first-principles joint density functional theory simulation, constrained to the X-ray data via a generalized penalty function, identifies an anatase-like structure as the more active, trained surface.

Authors:
; ; ; ; ; ; ; ; ; ; ; ;
Publication Date:
Research Org.:
Energy Frontier Research Centers (EFRC) (United States). Energy Materials Center at Cornell (EMC2)
Sponsoring Org.:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
OSTI Identifier:
1370457
DOE Contract Number:
SC0001086
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of the American Chemical Society; Journal Volume: 138; Journal Issue: 25; Related Information: Emc2 partners with Cornell University (lead); Lawrence Berkeley National Laboratory
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY

Citation Formats

Plaza, Manuel, Huang, Xin, Ko, J. Y. Peter, Shen, Mei, Simpson, Burton H., Rodríguez-López, Joaquín, Ritzert, Nicole L., Letchworth-Weaver, Kendra, Gunceler, Deniz, Schlom, Darrell G., Arias, Tomás A., Brock, Joel D., and Abruña, Héctor D. Structure of the Photo-catalytically Active Surface of SrTiO 3. United States: N. p., 2016. Web. doi:10.1021/jacs.6b03338.
Plaza, Manuel, Huang, Xin, Ko, J. Y. Peter, Shen, Mei, Simpson, Burton H., Rodríguez-López, Joaquín, Ritzert, Nicole L., Letchworth-Weaver, Kendra, Gunceler, Deniz, Schlom, Darrell G., Arias, Tomás A., Brock, Joel D., & Abruña, Héctor D. Structure of the Photo-catalytically Active Surface of SrTiO 3. United States. doi:10.1021/jacs.6b03338.
Plaza, Manuel, Huang, Xin, Ko, J. Y. Peter, Shen, Mei, Simpson, Burton H., Rodríguez-López, Joaquín, Ritzert, Nicole L., Letchworth-Weaver, Kendra, Gunceler, Deniz, Schlom, Darrell G., Arias, Tomás A., Brock, Joel D., and Abruña, Héctor D. 2016. "Structure of the Photo-catalytically Active Surface of SrTiO 3". United States. doi:10.1021/jacs.6b03338.
@article{osti_1370457,
title = {Structure of the Photo-catalytically Active Surface of SrTiO 3},
author = {Plaza, Manuel and Huang, Xin and Ko, J. Y. Peter and Shen, Mei and Simpson, Burton H. and Rodríguez-López, Joaquín and Ritzert, Nicole L. and Letchworth-Weaver, Kendra and Gunceler, Deniz and Schlom, Darrell G. and Arias, Tomás A. and Brock, Joel D. and Abruña, Héctor D.},
abstractNote = {A major goal of energy research is to use visible light to cleave water directly, without an applied voltage, into hydrogen and oxygen. Although SrTiO3 requires ultraviolet light, after four decades, it is still the “gold standard” for the photo-catalytic splitting of water. It is chemically robust and can carry out both hydrogen and oxygen evolution reactions without an applied bias. While ultrahigh vacuum surface science techniques have provided useful insights, we still know relatively little about the structure of these electrodes in contact with electrolytes under operating conditions. Here, we report the surface structure evolution of a n-SrTiO3 electrode during water splitting, before and after “training” with an applied positive bias. Operando high-energy X-ray reflectivity measurements demonstrate that training the electrode irreversibly reorders the surface. Scanning electrochemical microscopy at open circuit correlates this training with a 3-fold increase of the activity toward the photo-induced water splitting. A novel first-principles joint density functional theory simulation, constrained to the X-ray data via a generalized penalty function, identifies an anatase-like structure as the more active, trained surface.},
doi = {10.1021/jacs.6b03338},
journal = {Journal of the American Chemical Society},
number = 25,
volume = 138,
place = {United States},
year = 2016,
month = 6
}
  • A major goal of energy research is to use visible light to cleave water directly, without an applied voltage, into hydrogen and oxygen. Although SrTiO 3 requires ultraviolet light, after four decades, it is still the "gold standard" for the photo-catalytic splitting of water. It is chemically robust and can carry out both hydrogen and oxygen evolution reactions without an applied bias. While ultrahigh vacuum surface science techniques have provided useful insights, we still know relatively little about the structure of these electrodes in contact with electrolytes under operating conditions. Here, we report the surface structure evolution of a n-SrTiOmore » 3 electrode during water splitting, before and after "training" with an applied positive bias. Operando high-energy X-ray reflectivity measurements demonstrate that training the electrode irreversibly reorders the surface. Scanning electrochemical microscopy at open circuit correlates this training with a 3-fold increase of the activity toward the photo-induced water splitting. A novel first-principles joint density functional theory simulation, constrained to the X-ray data via a generalized penalty function, identifies an anatase-like structure as the more active, trained surface.« less
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  • Epitaxial oxide heterostructures are of fundamental interest in a number of problems ranging from oxide electronics to model catalysts. The epitaxial CoO/SrTiO{sub 3} (001) heterostructure on Si(001) has been recently studied as a model oxide catalyst for water splitting under visible light irradiation (Ngo et al., J. Appl. Phys. 114, 084901 (2013)). We use density functional theory to investigate the valence band offset at the CoO/SrTiO{sub 3} (001) interface. We examine the mechanism of charge transfer and dielectric screening at the interface and demonstrate that charge transfer is mediated by the metal-induced gap states in SrTiO{sub 3}, while the dielectricmore » screening at the interface is largely governed by the ionic polarization of under-coordinated oxygen. Based on this finding, we argue that strain relaxation in CoO plays a critical role in determining the band offset. We find that the offsets of 1.36–1.10 eV, calculated in the Schottky-limit are in excellent agreement with the experimental value of 1.20 eV. In addition, we investigate the effect of the Hubbard correction, applied on the Co 3d states, on the dipole layer and potential shift at the interface.« less
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